Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

Question # 1

Q no:7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²

Ans 1: Kinetic Energy :
The energy possessed by a body due to its motion is called kinetic energy.
Derivation:
Let a body of mass m is moving with velocity V. An opposing force F actingthrough a distance S brings it to rest. The body possesses kinetic energy and is capable to do work against opposing force F until all of its kinetic energy used up.
K.E of the body = Work done by it due to motion
K.E - FS
Vi = V
Vf =0
F = ma
a =-f/m
Since motion is opposed, hence , a is negative. Using 3rd equation of motion
2as =Vf² - Vi²
2 (-F/m)S =0² - V²
FS = +1/2 mv²
As we know that K.F is equal to the work done.
K.E =1/2 mv² ( proved )

Question # 2

Explain the mass-energy equation

Ans 1: Einstein predicted the interconversion of matter and energy. According to him, a loss in the mass of a body provides a lot of energy. This happen in the nuclear reaction. The relation between mass m and energy E is given by Einstein's mas-energy equation
E=mc²
Where c is the speed of light( 3*10⁸ ms^-1)
Ans 2: Significance; the above equation shows that tremendous amount of energy can be obtained from sample quaintly of matter. It happens that matter is highly concentrated form of energy
Ans 3: Uses: the process of getting the energy from our nuclear power plants is based on the above equation. The process is taking place on the sun and stars for the last millions of yeas. Only a very small fraction of the suns energy reaches the earth. This very small fraction of the suns energy is responsible for life on the earth.

Question # 3

Define work. when a force do work? explain

Ans 1: Work: work is said to be done when a force acts on a body and moves it in the direction of the force.
Recognition of work: the question raised how much work is done? naturally, greater is the force acting on a body longer is the distance moved by it, larger would be work done
" work is done when a force acting on a body displaces it in the direction of force".
Ans 2: Quantity: work is scaler quantity
Ans 3: Dependence; it depends on the force acting on the body, displacement of the body and angle between them.
Ans 4: unit: its unit is joule(J)
Ans 5: Definition: if one newton force act on the body it covers one meter distance in the direction of force, then its work will be one joule
1J= 1N*1m

Question # 4

What is energy converter ?

Ans 1: Energy converter : an energy converter is a device in which a part of energy taken by the system is converted into useful work. Remaining energy is dissipated as heat energy, sound energy, noise into the environment
Ans 2: Important energy converters: here are some most important energy converters
1. Electric lamp
2. Energy saver lamp
3. Vehicle running with constant speed on a level road
4. power station

Question # 5

Explain different kind of energy

Ans 1: Types of energy: there are number of forms of energy.
- Mechanical energy: the energy of a body both due to its position or due to its motion is called the mechanical energy e.g.wind ,water running down in stream etc. possess mechanical energy.
- Heat energy: The energy obtained due to burning of fuel is called heat energy. it obtained from the sun, or from the electric energy. It may also be obtained by burning of fuel. The main source of heat is the sun.
Ans 2:
- Electrical energy: the energy due to flowing charges is called electrical energy. It is obtained from batteries and generators. It is used to run electric lamps, household appliance.
- Sound energy: energy carried by sound waves is called sound energy. The sound waves are mechanical waves. These are produced by vibrating bodies. e.g, vibrating string and flute
Ans 3:
- Light energy: Light consists of electromagnetic waves, which posses energy it is called " light energy". The main source of light energy is the sun. it is also obtained by burning candles, bulbs, fluorescent tubes and burning fuel.
- Chemical energy: there are chemical reactions which produce energy. It is called chemical energy. the electrical energy obtained from batteries is due to chemical reactions inside batteries e.g, burning of coal, natural gas and wood in air is chemical reaction which release energy as heat and light
Ans 4: Nuclear energy: due to nuclear reactions energy is obtained called nuclear energy. The most famous nuclear reactions are "fission" and Fusion". Fusion nuclear reactions take place in the sun. The nuclear energy is obtained in the form of heat.

Question # 6

What is efficiency? explain working of an ideal system.

Ans 1: Efficiency: efficiency of a system is the ration of required form of energy obtained from a system as output to the total energy given to it as input.
Ans 2: Ideal system: an ideal system is that which gives an output equal to the total energy used by it. In other words, its efficiency is 100%. People have tried to design a working system that would be 100% efficient. But practically such a system does not exist. Every system meet energy losses due to friction that causes heat, noise etc. There are not the useful forms of energy and go waster . This means we cannot utilize all the energy given to working system . The energy in the required form obtained from a working system is always less than energy given to it as input.

Question # 7

Write a note on energy a nd environment

Ans 1: Sources; environmental problems such as pollution that consist of noise , air pollution and water pollution may arise by using different sources of energy such as:
- Fossil fuels
- Nuclear energy
Ans 2: Pollution: polliton is the change in quality of environment that can be harmful and unpleasent for living things.
Thermal pollution: a temperature rise into the environment that disturbs life is called thermal pollution.
Effects:
- Thermal pollution upsets the balance of life.
- It endangers the survival of many species
Ans 3: Air pollutants: Air pollutants are unwanted and harmful. Natural processes such as volcanic eruptions, forest fires and dust storm add pollutant to the air. These pollutants rarely build up to harmful levels. On the other hand the burning fuel and solid wastes in homes, automobiles' and factories release harmful amount of air pollutants
Ans 4: Pollution from fission plans: al power plants produce waste heat, but fission plants produce the most. The heat released into a lake , a river , or an oven upsets the balance of life in them. Unlike other power plants , nuclear power plants don't produce carbon dioxide. But they do produce dangerous radioactive wastes.
Ans 5: Laws; in many countries government have passed laws to control air pollution. Some of these limit the amount of pollution that power plants , factories ad automobiles are allowed to give off. To meet this condition for automobiles , new cars have catalytic converts. These devices convert some polluting gases. The use of lead free petrol has greatly reduced the amount of lead in the air. Engineers are working to improve new kinds of car engines that use electricity or energy sources other than diesel and petrol. Many individual communities have laws which protect their areas from pollution. Individuals can help to control arir pollution simply y reducing the use of card and other machines that burn fuel. Sharing rides and using public transportation ar the way to reduce the number of automobile's in use.

Question # 8

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

Ans 1: Potential Eenergy :
The energy possessed by a body due to its position is known as its potential energy.
Explanation:
Stored water possesses potential energy due to its height . A hammer rasisedup to some height has the avilityto do word because it possesses potential energy. Astretchedbow has potential energy due itsStretched position. When released , the stored energy of the bow is called elastic potential energy
The potential energy possessed by a hammer is due to its height. The energy present in a body due to its height is called gravitational potential energy.
Derivation
Let a body of mass m be raised up through height h from the ground. The body will acquire potential energy equal to the work done in lifting it to height h.
Thus
potential energy P.E = F x h
=w xh
= mg x h
P.E = mgh

Question # 9

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Ans 1: M= 200kg
h= 6 m
t= 10s
power of the pump = p=?
Since
F= w
= mg
200 x 10
=2000n
As we know that
p=w/t =F x s/t
But putting the values , we have
p= 2000 x6/10
p=m12000/10
P = 1200 W Ans

Question # 10

Q no: 7(A) Write is the uses of Wind Energy.?

Ans 1: Wind Energy:
Wind energy has used as a source of energy for centuries. It has powered sailing ships across the oceans . It has been used by windmills to grind grain and pump water. More recently , wind power is used to turn wind turbines. When many wind machines are grouped together on wind farms , they can generate enough power to operate a power plant. In the United stated , some wind farms generate more than 1300 MW of electricity a day. In Europe, many wind farms routinely generate hundred megawatts or more electricitya day

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Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

9th Class English Medium Subjects

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Online Long Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Physics (New Book) - 9th Class Physics Chapter 6 Long Question Preparation

Q no:7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²

Explain the mass-energy equation

Define work. when a force do work? explain

What is energy converter ?

Explain different kind of energy

What is efficiency? explain working of an ideal system.

Write a note on energy a nd environment

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Q no: 7(A) Write is the uses of Wind Energy.?

Prepare Complete Set Wise Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Set 1

Set 2

9th Class Physics Chapter 6 Long Question Preparation - Set 1

Q no:7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²

Explain the mass-energy equation

Define work. when a force do work? explain

What is energy converter ?

Explain different kind of energy

What is efficiency? explain working of an ideal system.

Write a note on energy a nd environment

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Q no: 7(A) Write is the uses of Wind Energy.?

9th Class Physics Chapter 6 Long Question Preparation - Set 2

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

Define work. when a force do work? explain

Q no: 7(A) Write is the uses of Wind Energy.?

Write and explain energy conversion processes involved in producing of electricity

What is energy converter ?

Write a note on energy a nd environment

Define potential energy, explain its types

What is meant by renewable sources of energy?

Explain different kind of energy

Q no:7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²

9th class Physics Chapter 6 Long Q's (English Medium)

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